1. Field of the Invention
The present invention relates to a method of synthesis of silicone-polyether copolymers. This method utilizes a catalyst which promotes ring-opening polymerization of a variety of heterocyclic, epoxide ring containing monomers at room temperature. The invention also relates to the silicone-polyether compositions.
2. Technology Review
Silicones have been used in cosmetic formulations for over 30 years. Silicone surfactants, especially silicone-polyether copolymers are widely used components in these cosmetic formulations. Until recently, the most important silicones used for these applications were poly(dimethylsiloxanes). Poly(dimethylsiloxane) emulsions when used in cosmetic preparations, improve the rub out of creams and lotions. They act as glossing agents in hair care products and give a silk-like feel to the skin. The main disadvantage of these poly(dimethylsiloxanes), especially those with higher molecular weights, is their poor compatibility with cosmetic oils. Further, since these compounds are hydrophobic, they cannot easily be used in aqueous formulations unless they are emulsified.
Silicone surfactants derived from poly(dimethylsiloxanes) display better compatibility with cosmetic oils and/or improved water solubility depending on the modifying groups that are attached to the poly(dimethylsiloxane) backbone. These materials have been traditionally prepared by the condensation of terminal functionalized silicones (poly(dimethylsiloxanes)) with similarly functionalized polyethers. Examples of such syntheses can be found in the following patents: U.S. Pat. No. 2,834,748; U.K. 892,819; U.K. 954,041; U.K. 107,156; U.S. Pat. No. 2,868,824; French 1,179,743; Belg. 603,552; Belg. 603,832; U.K. 1,038,348; U.K. 1,073,368; and Belg. 627,281.
Although the prior art includes many examples of preparing these materials by condensation reactions, there appear to be no citations in the literature describing the ring-opening polymerization of epoxide rings by catalysis used for this purpose.
Co-pending, commonly-assigned U.S. application No. 07/934,584 filed Aug. 24, 1992 discloses a cobalt-based catalyst which promotes ring-opening polymerization of a variety of heterocyclic epoxide ring-containing monomers and polymers.
Catalytic agents which have been used to catalyze the ring opening polymerization of various heterocyclic compounds, particularly epoxides, include acids, bases, and certain metal complexes such as, for example, organoboron compounds, FeCl.sub.3, ZnEt.sub.2 /H.sub.2 O, AlEt.sub.3 /H.sub.2 O, and aluminoporphrins. Reference is made, for example, to Ivin and Saegusa, Ring Opening Polymerization, Vol. 1, Elsevier Appl. Sci. Pub., New York 1984, p. 185; and to May and Tanaka, Epoxy Resins Chemistry and Technology, Marcel Dekker, Inc., New York, 1973, p. 283.
Epoxy monomers may be polymerized by either UV radiation or heat. Polymerization by UV radiation involves the use of a photocatalyst that, when irradiated with UV light, forms an acid that catalyzes the epoxide. Such reactions are taught by Eckberg in U.S. Pat. No. 4,279,717 and Crivello in U.S. Pat. No. 4,617,238.
Polymerization by heat involves the simple step of heating the epoxy monomers to a temperature of 120.degree. C. or greater, causing the oxirane rings to open and react. Specific reference is made to E. P. Plueddumann and G. Fanger, Epoxyorganosiloxanes, Journal of the American Chemical Society, vol. 81, pp. 2632-2635, 1959.
Platinum-containing catalysts are highly useful catalysts in hydrosilation reactions, i.e., the addition of Si--H containing compounds to olefin and acetylenic bonds. Reference is made to Aylett, Organometallic Compounds. Vol. 1, John Wiley, New York, 1979, p. 107 and to Speier, Adv. in Org. Chem., Vol. 17, p. 407, 1974. It is further known in the art that platinum catalysts will catalyze the hydrosilation reaction between ethylenically unsaturated organic epoxy monomers and Si--H containing compounds. Such reactions are described, for example, in copending, commonly assigned application Ser. No. 332,646, filed Apr. 3, 1989.
The use of platinum catalysts to promote ring opening of heterocyclic monomers provides numerous advantages over catalysts presently used in their polymerization. These advantages include the use of low levels of platinum catalysts and the low tendency of catalyst residues to induce color, oxidative instability in the final cured resin, or corrosion to metals in contact with the resin. Furthermore, with silicones, the platinum catalysts are less prone to cause reversion of the silicone polymers to cyclic siloxanes.
Dicobaltoctacarbonyl, Co.sub.2 (CO).sub.8, has been widely used as a catalyst for the hydrogenation of olefins, for which reference is made to (a) Major, Horvath, and Pino, J. Molecular Catalysis, 1988, 45, 275, (b) Ungvary and Marko, J. Organometal. Chem., 1981, 219, 397, (c) Ungvary and Marko, Organometallics, 1982, 1, 1120, and (d) Wender, Levine and Orchin, J. Am. Chem. Soc., 1950, 72, 4375; the hydroformulation of olefins, for which reference is made to (a) Wender, Sternberg and Orchin, J. Am. Chem. Soc., 1953, 75, 3041, and (b) Orchin, Kirch and Goldfarb, J. Am. Chem. Soc., 1956, 78, 5450; and the hydrosilation of olefins, for which reference is made to (a) Hilal, Abu-Eid, Al-Subu and Khalaf, J. Molecular Catalysts, 1987, 39, 1, (b) Harrod and Chalk, J. Am. Chem. Soc., 1965, 87, 1133, (c) Chalk and Harrod, J. Am. Chem. Soc., 1967, 89, 1640, and (e) Baay and MacDiarmid, Inorg. Chem., 1969, 8, 986. In addition, there is one report in the literature describing the catalysis by Co.sub.2 (CO).sub.8 of the ring-opening polymerization of a heterocyclic compound (Chalk, J. Chem. Soc., Chem. Commun., 1970, 847). Chalk has reported that when Co.sub.2 (CO).sub.8 was used as a hydrosilation catalyst employing tetrahydrofuran as a solvent, poly(tetramethylene oxide) resulting from the ring-opening of the THF was isolated.
Harrod and Smith similarly observed that THF could be ring-opened under hydrosilation conditions using iridium-containing catalysts (Harrod and Smith, J. Am. Chem. Soc., 1970, 90, 2699). However, polymerization was not observed and only the olefin derived from transfer of the trialkylsilyl group to the oxygen of THF followed by ring opening and elimination, was obtained.
In addition, Co.sub.2 (CO).sub.8 -mediated ring-opening reactions of carbon monoxide with epoxides and other heterocyclic compounds has recently been studied, regarding which reference is made to (a) Alper, Arzoumanian, Petrinani and Saldana-Maldonado, J. Chem. Soc., Chem. Commun., 1985, 340, (b) Alper and Calet, Tetrahedron Letters, 1985, 26. 5735, (f) Seki, Hidaka, Murai and Sonoda, Angew. Chem., 1977, 89, 196, (g) Murai and Sonoda, Angew. Chem., 1979, 18, 837, (h) Murai, Hatayama, Murai and Sonoda, Organometallics, 1983, 2, 1883, (i) Chatani, Fujii, Yamasaki, Murai and Sonoda, J. Am. Chem. Soc., 1986, 108, 7361, (j) Murai, Kato, Murai, Hatayama and Sonoda, Tetrahedron Letters, 1985, 26, 2683, and (k) Murai et al., J. Am. Chem. Soc., 1989, 111, 7938. These reactions require high pressure and high temperatures, and polymerization was not observed in any of these studies.